1. Field of the Invention
The present invention relates to an optical transmission device, an optical transmission/reception device, a control method, and a control program. More specifically, the present invention relates to an optical transmission device which outputs transmission data by converting it into optical signals, an optical transmission/reception device, a control method, and a control program.
2. Description of the Related Art
Recently, there has been a wide spread of an optical transmission/reception device which is connected to an optical communication net that transmits a vast amount of information at a high speed for having optical communications mutually with other communication apparatuses connected to the optical communication net. The optical transmission/reception device is provided with a transmission-side circuit which converts main signal data outputted from a host-side device into optical signals and transmits the optical signals to the communication apparatuses on the optical communication net side via an optical fiber.
The transmission-side circuit includes a laser diode, for example, as a light source for generating laser beams, and an electric absorption (EA) optical modulator which modulates the generated laser beams. It is desired to integrate those modules, to reduce the power consumption, etc.
Under such circumstance, an optical transmission device including a wavelength variable light source, and an EA (electric absorption) modulator, and a thermoelectric cooler is proposed in Japanese Unexamined Patent Publication 2009-81512 (Patent Document 1), for example. The optical transmission device is structured to input an EA bias to the EA modulator from a control unit, and to modulate light outputted from the wavelength variable light source according to the modulation characteristic in accordance with the EA bias. Further, the control unit controls the temperature of the thermoelectric cooler so that the EA temperature information showing the temperature of the EA modulator becomes the target temperature.
Further, Japanese Unexamined Patent Publication 2004-296988 (Patent Document 2) discloses a laser diode having an electric absorption modulator which detects the temperature of the laser diode by a thermistor, and increases the amount of heat generated by a heater so as to have an optimum temperature when the outside temperature is low while decreasing the amount of heat when the temperature is optimum. The laser diode having the electric absorption modulator controls the temperature of the laser diode without using an electric cooler element.
Further, Japanese Unexamined Patent Publication Hei 11-126939 (Patent Document 3) discloses a temperature control device of a semiconductor laser module (LD module) including a TEC (thermoelectric cooler), PD (photodiode), a temperature detection element (thermistor), an LD chip, and the like housed inside a package. The temperature control device is structured not to control the temperature of the LD chip when the outside temperature Ta is within a guaranteed temperature range of the semiconductor laser and not to apply a Peltier current to the TEC.
Further, it is depicted in NTT Photonics Laboratories, Wataru Kobayashi, et al., “Low Power Consumption 1.55 μm EADFB Laser”, NTT Technical Review, November 2010 (Vol. 22 No. 11), pp. 69-73 (Non-Patent Document 1) that the property of a wide temperature range is improved even in an uncooled action (uncontrolled temperature) by using indium-gallium-aluminum arsenic based semiconductor material (Al based material) as a material for fabricating an EA modulator integrated DFB (distributed feedback) laser (EA-DFB laser).
However, the optical transmission device depicted in Patent Document 1 determines a threshold value (value of the EA temperature) based on the number of FIT (failure in time), the power consumption, and the EA temperature, and controls the temperature control current by having the temperature and the wavelength of the EA modulator as input information. The optical transmission device is structured to control the temperature control current within a range of TA<Tn<Tb (upper limit temperature Ta, target temperature Tn, lower limit temperature Tb), so that the power is consumed.
Further, while Patent Document 2 discloses a technique which loads a heat generator so as to control the temperature of the laser diode to be within a defined temperature range set in advance, it is designed to control the amount of heat generated by the heat generator.
Furthermore, while Patent Document 3 mentioned above discloses a technique which includes a thermistor whose resistance value changes according to the temperature of the semiconductor laser module (LD chip), and controls the temperature of the LD chip according to the temperature of the LD chip so that the temperature of the LD chip falls within a specific range (guaranteed range), the output property of the LD chip is changed with a change in the temperature of the guaranteed range.
It is therefore an exemplary object of the present invention to provide an optical transmission device, an optical transmission/reception device, a control method, and a control program, which can acquire a fine light output property of the optical signals to be outputted.